This invention provides compositions having improved rheological properties based on polycarbonate with rearrangement structures and cyclic and linear oligomers, and shaped articles and extrudates of these polycarbonate compositions.
The process for polycarbonate synthesis is generally known and is described in numerous publications.
EP-A 0 517 044, WO 2006/072344 and EP-A 1 609 818 and documents cited there describe, for example, the interfacial and the melt process for the preparation of polycarbonate.
The preparation of aromatic oligo- and polycarbonates by the melt transesterification process is known in principle from the literature and has been described earlier, for example, in the Encyclopedia of Polymer Science, vol. 10 (1969), Chemistry and Physics of Polycarbonates, Polymer Reviews, H. Schnell, vol. 9, John Wiley and Sons, Inc. (1964) and in DE-C 10 31 512, U.S. Pat. No. 3,022,272, U.S. Pat. No. 5,340,905 and U.S. Pat. No. 5,399,659.
It is known that low molecular weight constituents (oligomers, cyclic structures or additives) in thermoplastics lead to a reduction in the melt viscosity and therefore act as inherent plasticizers. Thus, EP-A 0953605 describes the use of cyclic aromatic carbonates as flow improvers and agents for improving the shape transferability of linear aromatic polycarbonates.